Dispatch a new event chrome.contextMenus.onClicked.
Disallow onclick create parameter for event pages.
Fix onClickData, which had incorrect types and missing fields.
BUG=
123366
TEST=Register a chrome.contextMenus.onClicked handler in an event page (adding the menu items upon chrome.runtime.onInstalled). Check that it fires.
Committed:
https://src.chromium.org/viewvc/chrome?view=rev&revision=140112